Summary
Highlights
The circulatory system, also known as the cardiovascular system, is essential for all body systems, acting as a delivery network for oxygen, nutrients, and hormones, and for removing waste. It supports the respiratory, digestive, muscular, endocrine, immune, excretory, nervous, and skeletal systems.
There are two main types of circulation: pulmonary circulation, which transports deoxygenated blood from the heart to the lungs to pick up oxygen and return to the heart, and systemic circulation, which carries oxygenated blood from the heart to the body for cellular respiration and returns deoxygenated blood to the heart.
The heart, located slightly to the left in the chest cavity, is a fist-sized pump made of cardiac muscles. It has four chambers: the right atrium and ventricle, which handle deoxygenated blood to the lungs, and the left atrium and ventricle, which receive oxygenated blood from the lungs and pump it to the body. Four valves ensure one-way blood flow, preventing backflow.
Blood vessels include arteries, which carry blood away from the heart under high pressure with thick, elastic walls; veins, which return blood to the heart with thinner walls and valves to prevent backflow; and capillaries, tiny, one-cell-thick vessels that connect arteries and veins, facilitating the exchange of gases, nutrients, and wastes with tissues.
Blood flows from the heart into arteries, then to arterioles, capillaries, venules, and finally veins, returning to the heart. The heart's four chambers and the septum keep oxygenated and deoxygenated blood separate, ensuring efficient oxygen delivery and waste removal. Valves maintain distinct one-way paths for both types of blood.
Blood consists of plasma (mostly water, carrying cells, proteins, hormones, and nutrients), red blood cells (carrying oxygen and carbon dioxide), white blood cells (fighting infections), and platelets (aiding in blood clotting). Blood transports metabolic waste to organs for processing and excretion, carries electrolytes, glucose, fatty acids, hormones, and immune system components.